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Alexandre PEDINIELLI, Marthe Laguarrigue, Sarah Mrejen, Florence Rossant, Ramin Tadayoni, Alain Gaudric, Valerie Krivosic, Michel Paques; Photoreceptor anisotropy in macular oedema and MacTel : a multiangle OCT study. Invest. Ophthalmol. Vis. Sci. 2016;57(12):4248. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
Reflectivity of outer structures of cone photoreceptors is related to the angle of incident light, which is called the optical Stiles-Crawford effect. Here we used multiangle optical coherence tomography (MAOCT) to document directional variations of the reflectance of photoreceptor in eyes with resolved macular oedema or macular telangiectasias (MacTel).
Observational, two center study. In 9 controls and in 4 eyes with resolved macular oedema from retinal vein occlusion and 17 eyes of 10 patients with MacTel 2, three registered OCT scans (Spectralis, Heidelberg Engineering, Germany) were acquired coaxially and 2.3° off axis horizontally on both sides of the optical axis. Fusion, color-coded and differential images were generated using an ImageJ-based routine.
In control eyes, coaxial scans and fusion images were similar, while differential images showed diffuse anisotropy in the Henle fiber layer, the cone outer segment tip (COST) line and to a lesser extent the inner/outer segment (IS/OS) line. In diseased eyes, the length of the discontinuity of the COST line in the macula was reduced on fusion images by a mean of 8% (range, 0-38%); accordingly, differential images showed patchy areas of altered anisotropy of the COST line (length, 139 to 890µm) in all RVO eyes and in 10 out of 16 MacTel eyes. Among the latter, two showed evidence of photoreceptor disarray, that is, adjacent photoreceptors with divergent pointing. Overall, reflectivity changes of the IS/OS paralleled those of the COST, while there were no changes in the anisotropy of the Henle fiber layer.
MAOCT shows that changes in photoreceptor anisotropy is common following macular edema and MacTel, which may participate to the apparent disruption of the outer retinal reflectance. Such anisotropy changes may result from photoreceptor disarray and/or alteration of the optical Stiles-Crawford effect. In two cases, we found clear evidence of photoreceptor disarray, indicating that phototropism may be chronically altered. Although the functional consequences of altered anisotropy remains to be determined, modifications of their incidence-sensitivity curve and hence some degree of visual impairment is likely.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
Three OCT scans (top row; arrows shows direction of incident light) were combined to generate differential and fusion scans in a case of resolved macular edema. Color coding highlights spots of altered anisotropy (arrows).
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